1. Field of the Invention
The present invention relates to a circuit assembly advantageously used in e.g. a battery pack of a notebook computer, mobile phone, etc. The present invention also relates to a battery pack provided with such a circuit assembly. Further, the present invention relates to a method of making such a circuit assembly.
2. Description of the Related Art
Conventionally, various types of battery packs are used for portable electronic devices such as notebook computers and cellular phones. These battery packs are removable and incorporate a lithium battery, for example.
FIG. 14 is a partial cut-away view showing the inside of a typical battery pack provided with a circuit assembly 10 the plan view of which is shown in FIG. 15. The circuit assembly 10, together with a number of batteries 2, is accommodated in the box-like, rectangular housing 1 of the battery pack P. A connector C and several electronic components E are mounted on the circuit assembly 10. The batteries 2 are connected to the circuit assembly 10. The circuit assembly 10 regulates the charging or discharging of the batteries 2 and controls the passage of electric signals to or from an external circuit.
When the battery pack P is used for a notebook computer for example, there is an upper limit to the size of the housing 1 due to the restricted accommodation space of the computer. Accordingly, the housing 1 may not provide a large internal space for the parts other than the batteries 2.
In light of this, as shown in FIG. 15, the circuit assembly 10 includes first and second substrates 11, 12 to be suitably accommodated in the housing 1. The two substrates 11 and 12 are electrically and mechanically connected to each other via a joint member 41 which is bendable. This allows the circuit assembly 10, when accommodated in the housing 1, to be bent at right angles, as seen from FIG. 14, with the first substrate 11 being arranged along a shorter side wall of the housing 1 and the second substrate 12 being arranged along a longer side wall of the housing 1.
The first substrate 11 and the second substrate 12 are formed with a wiring pattern 42 on one or both surfaces of the respective substrates. Being connected to the wiring pattern 42, the connector C and the electronic components E are mounted on the substrates 11 and 12, respectively. Each substrate 11, 12 has an end portion provided with a number of terminals 43 to which the wiring pattern 42 is connected. The leads (to be mentioned below) of the joint member 41 are also connected to the terminals 43.
FIG. 16 is a perspective view showing the joint member 41. The joint member 41 includes a plurality of leads 44 arranged in parallel to each other, and insulating films 45 sandwiching the leads 44 from above and below. The leads 44 are configured to have a plateau in their middle portions. The ends of each lead 44 are connected to the terminals 43 formed on the substrates 11 and 12, whereby the substrates 11 and 12 are electrically and mechanically connected to each other.
In the above-described joint member 41, the regularly spaced leads 44 are held in place rather unstably by the pressing force of the two films 45. This arrangement, however, may permit the leads 44 to shift in position between the films 45 and even come into contact with each other when the joint member 14 is bent or vibrated for example. Unfavorably, when the leads 44 are short-circuited, the proper function of the circuit assembly 10 will fail.